The pathogen Bordetella pertussis elaborates a number of virulence factors during the course of disease. The production of many of these factors is coordinately regulated through the two component regulatory locus bvg, in response to environmental stimuli. Our previous work has identified a number of previously uncharacterized proteins which are regulated by this locus and are produced together with the more thoroughly studied virulence determinants flamentous hemagglutinin and pertussis toxin. Two of these determinants are Tcf and Vag8. B. pertussis mutants which no longer produce Tcf are defective in their ability to colonize mice in an aerosol challenge model. The gene endcoding Tcf has been cloned and sequenced. The mature form of Tcf is a secreted 34kDa protein. This protein contains the three amino-acid motif RGD and is 16.5% proline. The expression of Tcf is unique to strains of B. pertussis, the other species of Bordetella do not appear to have the gene encoding Tcf. Vag8 is encoded by the vag-8 gene, previous work had indicated that a TnphoA insertion mutant defective in this protein neither colonized mice nor induced lymphocytosis. We have characterized this strain and determined that this mutant contains two insertions. One insertion is in a gene encoding a bvg regulated protein, this gene has been termed vag-8. The derived amino-acid sequence predicts that vag-8 encodes a 95kDa protein, Vag8. The C-terminal 30kDa of this protein has identity to the C-terminal 30kDa of pertactin. Thus, Vag8 has homology to a family of Bordetella proteins which we have termed "tailed secreted proteins". The C-termini of these proteins may function to export these proteins across the bacterial cell envelope. After export cleavage may occur with the mautre protein remaining attached to the cell surface, as is pertactin, or released into the supernatant as is Tcf. Unlike the other Tsps identified to date, Vag8 does not appear to be processed and thus remains cell associated. Our future studies will concentrate on the contribution of these proteins to the pathogenesis of B. pertussis.